The present invention relates to a process that reduces or compensates for stress between a slider and a supporter within a magnetic head assembly.
FIG. 4 illustrates a partial side view of a magnetic head within a hard disk drive. The magnetic head includes a slider 1 and a supporter 2. The slider 1 is made of a ceramic material that includes a magnetic element 4 positioned near a trailing edge B. The magnetic element 4 includes an MR head (read head) and an inductive head (write head). The MR head detects a leakage magnetic field from a hard disk by detecting a magnetoresistive effect. The inductive head includes a coil. The supporter 2 includes a load beam 5 and a flexure 6. The load beam 5 is made of a leaf springs material such as stainless steel and includes a hemispherical pivot 7. The hemispherical pivot 7 projects downward from the flexure 6 and biases the slider 1.
The flexure 6 is constructed of a thin leaf spring material such as stainless steel. The flexure 6 includes a fixed portion 6a and a tongue piece 6b. The slider 1 is fixed to the bottom surface of the tongue piece 6b by an adhesive layer 20. The top surface of the tongue piece 6b is pressed against the pivot 7. The slider 1 is attached to the bottom surface of the tongue piece 6b. Due to the elasticity of the tongue piece 6b, the slider 1 can change positions relative to the pivot 7.
The slider 1 is pressed toward a disk D by the elastic force produced by the load beam 5. The magnetic head is generally used in a hard disk drive of a contact start and stop (CSS) type. When the disk D is stationary, an ABS surface 1a of the slider 1 comes into contact with a recording surface of the disk D due to the elastic force generated by the load beam 5. When the disk D rotates, air flows between the slider 1 and the surface of the disk D in a rotating direction of the disk D. Accordingly, the ABS surface 1a of the slider 1 is biased upward by the airflow, and the slider 1 is carried above the surface of the disk D at a height or a spacing of xcex41.
As shown in FIG. 4, the slider 1 inclines. This inclination allows the leading edge A to be positioned at a higher position than the trailing edge B relative to the disk D as the magnetic element 4 passes above the disk D. In this configuration, the MR head of the magnetic element 4 reads magnetic signals from the disk or the inductive head writes magnetic signals to the disk D.
As shown in FIG. 5, a gap separates the slider 1 from the tongue piece 6b of the flexure 6. The distance h1 between the slider 1 and the tongue piece 6b receives the adhesive layer 20. The adhesive layer 20 is made of a thermosetting resin. In an adhering process, the adhesive layer 20 is disposed between the slider 1 and the flexure 6. UV curing is performed on the combination to temporarily fix the slider 1 to the flexure 6. Heat treatment is then applied to cure the adhesive layer 20, which affixes the slider 1 to the flexure 6.
Since the slider 1 and the flexure 6 have different coefficients of thermal expansion, there can be problems affixing the slider 1 to the flexure 6 by a heat treatment. The slider 1 can deform as the slider 1 is secured to the tongue piece 6b. The amount of deformation that can occur is proportional to a difference between the coefficients of thermal expansion of the slider 1 and the flexure 6, and is also proportional to a difference between the heat curing temperature and the room temperature.
In FIG. 5, the coefficient of thermal expansion of the flexure 6 is larger than that of the slider 1. Thus, when the slider 1 deforms the ABS surface 1a warps outward. As the ABS surface 1a warps outward, the spacing h1 is reduced or lost which adversely affects the output of the magnetic element 4 as the disk D rotates.
In some conventional magnetic heads, the thickness of the adhesive layer 20 cannot be adjusted, and the distance h1 between the slider 1 and the flexure 6 is not large enough to adequately absorb the stress. When the distance h1 is small, the adhesive layer 20 cannot adequately absorb the stress, and the deformation of the slider 1 during the heat curing process of the adhesive layer 20 cannot be suppressed.
When the distance h1 is too large, it is difficult to position the slider 1 in a parallel position to the flexure 6, and the slider 1 tends to be fixed in an inclined position. In such instances, the slider 1 cannot always be placed in a predetermined position. Thus, a spacing loss occurs and the slider 1 can collide with the surface of the disk D.
In addition, in some conventional magnetic head devices, the thickness of the adhesive layer 20 is not uniform, and the surface 20a of the adhesive layer 20 tends to undulate. In such instances, it is difficult to adequately secure the slider 1 to the flexure 6 through the adhesive layer 20.
Accordingly, presently preferred embodiments provide a magnetic head which is substantially free of the above-described problems. More specifically, the presently preferred embodiments provide a magnetic head in which an adhesive layer is disposed between the slider and the supporter. A gap or clearance of adequate size is maintained to reduce or compensate for the stress generated by different coefficients of thermal expansion of the slider and the supporter. In addition, the presently preferred embodiments provide a read and/or write apparatus having a magnetic head.
According to an aspect of the invention, a magnetic head includes a slider, a supporter, and an adhesive. The slider includes a magnetic element used for reading and/or writing. Preferably, the supporter has a different thermal expansion coefficient than the thermal expansion coefficient of the slider. An adhesive layer is disposed between the slider and the supporter. The adhesive layer includes particulate matter or components. The slider and the supporter are secured to each other by the adhesive layer. The particulate components preferably create a gap between the slider and the supporter. According to one presently preferred embodiment, the gap or clearance between the slider and the supporter is defined by the size of the particulate components within the adhesive.
Preferably, the adhesive layer disposed between the slider and the supporter can adequately absorb or transfer the stress induced by the different thermal expansion coefficients of the slider and the supporter. Thus, deformation of the slider during a heat curing process can be substantially reduced.
Since the particulate components are preferably mixed in the adhesive layer, an adhesive layer having uniform thickness can be used. Accordingly, a flat surface of the adhesive layer is easily created, and the slider is secured in a substantially parallel position to the supporter by the adhesive layer. Preferably, the size of the gap positioned between the slider and the supporter is within a range of about 20 to about 30 xcexcm. When the gap is smaller than about 20 xcexcm, the stress generated during the heat curing process by the thermal expansions of the slider and the supporter cannot always be adequately absorbed. When the gap is larger than about 30 xcexcm, it can be difficult to secure the slider in a substantially parallel position to the supporter.
In addition, some of the particulate components preferably have a cross-sectional size of about 20 to about 30 xcexcm in an area in which the slider and the supporter oppose each other. Accordingly, the height of the gap or distance between the slider and the supporter is preferably within the range of about 20 to about 30 xcexcm. In addition, some of the particulate components having a cross-sectional height or thickness of about 20 to about 30 xcexcm are preferably contained in the adhesive layer at about 5% weight to about 20% weight.
In addition, a Type D durometer hardness of the adhesive layer after heat curing is preferably within a range of about 50D to about 70D. The adhesive layer preferably has an adequate hardness. When the adhesive layer is too soft, it is difficult to secure the slider in a parallel position to the supporter. When the adhesive layer is too hard, the stress generated during the heat curing process by the thermal expansion of the slider and the supporter cannot always be adequately be absorbed.
The particulate components preferably include an inorganic filler and/or an organic filler. The inorganic or organic fillers also called as spacers, or a combination of inorganic and organic filler can comprise commercial fillers. In addition, at least the surfaces of some of the particulate components are preferably conductive. When such conductive particulate components are contained in the adhesive layer, the slider and the supporter are electrically coupled to each other. Accordingly, static or accumulated charges on the slider may be discharged to ground through the supporter.
In addition, the particulate materials or components are preferably comprised of a conductive metal. Alternatively, the particulate components can be comprised of an insulator, and surfaces of these particulate components can be conductive. The particulate components are preferably contained within the adhesive layer, which is disposed between the slider and the flexure. Thus, the gap or clearance having the predetermined size is positioned between the slider and the flexure, and the stress generated by the thermal expansion of the slider and the flexure may be adequately absorbed or transferred by the adhesive layer. Accordingly, the deformation of the slider may be controlled or preferably prevented in comparison to some conventional assemblies. In addition, the flat surface of the adhesive layer may be adequately formed, and the slider may be secured in a substantially parallel position to the flexure. Thus, spacing losses that can occur when the disk is driven can be reduced and a stable output can be obtained.
According to another aspect, a magnetic head comprises a slider having a magnetic element that reads and/or writes to a disk. Preferably, a supporter has a different coefficient of thermal expansion than the coefficient of thermal expansion of the slider. An adhesive layer is disposed between the slider and the supporter. A gap within a range of about 20 to about 30 xcexcm is provided between the slider and the supporter. The adhesive layer positioned within the gap is preferably comprised of an adhesive having a Type D durometer hardness after curing within a range of about 50D to about 70D.
In another aspect, preferably the particulate components are not mixed in the adhesive. However, the Type D durometer hardness of the adhesive layer after curing and the size of the gap between the slider and the supporter are within predetermined ranges. The stress that is generated during the heat curing by the thermal expansion of the slider and the supporter is preferably reduced by selecting a compensating adhesive. Accordingly, deformation of the slider may be controlled or substantially compensated by the adhesive.
When the distance between the slider and the flexure is within the range of about 20 to about 30 xcexcgm and the Type D durometer hardness of the adhesive layer after curing is within the range of about 50D to about 70D, the particulate components need not be contained in an adhesive layer. In this presently preferred embodiment, the gap or clearance between the slider and the flexure can adequately absorb the stress generated by the difference in thermal expansion coefficients between the slider and the flexure. Accordingly, deformation of the slider is substantially reduced, and a flat adhesive surface is formed. In addition, the slider may be fixed in a substantially parallel position to the flexure. Thus, spacing losses that can occur when the disk is driven can be reduced and a stable output can be obtained.
A magnetic read and/or write apparatus according to another presently preferred embodiment comprises a rotating unit, a head, and a drive device. Preferably, the rotating unit comprises a structure that moves across a recording medium. The driving device or driving means moves the magnetic head across the recording medium.
An adequately dimensioned gap is preferably created by the adhesive layer disposed between the slider and the supporter. The stress caused by the differences in thermal expansion coefficients of the slider and the supporter is preferably absorbed by the adhesive layer. In addition, a flat adhesive surface layer may be formed, and the slider may be easily positioned substantially parallel to the supporter. Accordingly, the slider can be carried above or across the recording medium with a predetermined spacing between the slider which improves the writing and the reading process of the disk.